Jet pulverizer



G. M. CROFT JET PULVERIZER April 26, 1960 3 Sheets-Sheet 1 Filed Sept. 22, 1953 INVENTOR George M Croft April 26, 1960 ca. M. CROFT JET PULVERIZER 3 Sheets-Sheet 2 Filed Sept. 22, 1953 lNVENTOR George M. Croft a 0 M a W 4 f is" 1 H aw i: ill] ,0 4* n .1 m." p a fi w a a .6 n u 8 v a m m w% an E Ill/l l I! I 4 a u. 1 m u w April 26, 1960 g b 2,934,276

JET PULVERIZER 4 Filed Sept. 22, 1953 S SheetS-Sheet 3 z I I 54 as 86 I 86 i I 6.7 6'6 70 50 I 4.9 I I l \\\I [I] l I I??? 1/ w Eg INVENTOR George M Croft United States Patent JET PULVERIZER George M. Croft, Fox Chapel Borough, Pa., assignor to Majac, Inc, Sharpsburg, Pa., a corporation of Pennsylvania Application September 22, 1953, Serial No. 381,676

16 Claims. (Cl. 241-40) This invention relates to a jet pulverizer for grinding and classifying solid particles. More particularly, this invention pertains to an impact pulverizer and power classifier for handling solid substances of varying nature with great flexibility and precision as to the size of the finished particles.

In the pulverizing and classifying of diverse solid substances such, for example, as graphite and coal, numbers of problems have arisen under prior practices. Not only does each kind of solid have its own characteristics but in many cases the grinding and classifying are diflicult or expensive, or both, to control. The uncertainty of control and resulting particle size or uniformity have been particularly acute in the grinding of solids to micron size, although many industrial substances require such fineness. Moreover, the resetting of a pulverizer to work to different specifications has entailed undue handling or difiiculty. And, in many cases, it has not been possible to standardize or provide sufiicient flexibility to handle various solid materials which otherwise would be suitable for impact grinding and classification.

In the present invention, the foregoing difliculties have been overcome. In a new pulverizer of this invention, great flexibility has been provided not only for purposes of adjustment relative to a single solid substance but also with respect to the adaptability of such a new pulverizer to relative standardization and employment with a wide variety of solid substances. Still further, in the new device of this invention, a sureness of control and economy of operation is obtainable with precision sizing and uniformity in the finished product. Other objects and advantages of this invention will be apparent from the following description and from the accompanying drawings, which are illustrative only, in which Figure 1 is a view in end elevation of a new jet pulverizer constituting an embodiment of this invention;

Figure 2 is a view in side elevation of the new construction shown in Figure 1;

Figure 3 is a view taken along line III--III of Figure 1;

Figure 4 is a view, partly in section, of the top of the classifier portion of the new pulverizer taken in the position shown in Figure 2; and

Figure 5 is an isometric view of a portion of a rotor arm used in the illustrated embodiment of this invention.

Referring to the drawings, a new pulverizer made in accordance with this invention may be provided with a base 10. Base 10 in turn may support a pair of opposed aligned grinding jets 11, an impact grinding chamber 12 and the structure thereabove. Each jet may comprise a casing 13 having a nozzle 14 extending axially thereinto through a packing gland 15. A coupling 16 at the outer end of each nozzle 14 enables ready connection of the nozzle to be made to a motive gas source, usually compressed air or steam. Each jet 11 is also provided with a barrel 17 in alignment with its respective nozzle 14. In each jet 11 the nozzle 14 and barrel 17 are axially and separately adjustable. A space 18 between the inner end of each nozzle 14 and the outer end of each barrel 17 constitutes an entry opening for particles of solid material to enter the jets along with the gas which acts to move the particles through the various circuits in the course of an operation of the new device. Access to the entry openings 18 which funnel material into the outer ends of the respective barrel 17 is provided through a branch opening 19 in each casing 13, such branch opening 19 communicating with the lower end of a respective return pipe 20. The upper end of each return pipe 20 is provided with an inlet 21 on respective and opposite sides of an inverted conical portion 22 at the bottom of a classifier 23.

Impact grinding chamber 12 is cubical and provided with a wear plate 24, walls 25 and a top 26. A cover 27 closes one side of chamber 12 and is removable for inspection or repair. A capped inspection opening 28 may be availed of to observe conditions within during operation. A base 29 supports a variable speed motor drive 3% which rotates a screw conveyor shaft 31 suitably mounted in bearings. A screw conveyor 32 within a tube 33 is rotated when the shaft 31 rotates to feed solid substances such as coal or graphite, for example, from a hopper 34 into chamber 12 through opening 35.

In operation, the stream movement into and out of chamber 12 is so great that the material therein including the fresh feed of solids supplied by conveyor 32 through opening 35 passes out of chamber 12 through a discharge pipe 36. In the embodiment shown, discharge pipe 36 is vertical and is ofiset from the common axis of the jets 11. The axis of discharge pipe 36 is coincident with the vertical axis of classifier 23 in the new jet pulverizer, the discharge end 37 of pipe 36 being in direct communication with the bottom of classifier 23 at the base of the inverted conical portion 22 thereof. An additional gas chamber 38 is concentric relative to the upper part 37 or" discharge pipe 36. The top of chamber 38 also opens fully and directly into the bottom of portion 22. An inlet pipe 39 supplies additional gas, preferably in the form of the same gas as the motive fluid to nozzles 14, to the new device both for transport of solids and for aid in classification.

A cylindrical wall 41 in classifier 23 of the new jet pulverizer surmounts portion 22 and is closed at the top by a head 41 having an outlet opening 42 for ground particles of proper size which constitute the final product of an operation of the new device. Such final product passes out through outlet 42 and pipe bend 43 to be conducted to storage or place of use. Access doors 44 and 45 may be provided in the classifier portion of the new device for opening in the event such access becomes desirable between operations. During operation, the new device is sealed so that the various streams of solid particles and gas passing through the various circuit portions of the new device will not leak into the space surrounding the new device.

A plurality of partitions 46, 47 and 48 are arranged in concentric manner within wall 40. Thereby, an annular return passage 49 for the generally downward movement of oversize particles exists between partition 46 and wall as, a further annular return passage 50 exists be tween partitions 46 and 47 and still further annular return passage 51 exists between partitions 47 and 48. These partitions may be stayed to one another and to wall 40 by staybolts S6. Further support for such partitions is provided by gusset plates 52 arranged at intervals around the lowermost edges thereof, said gusset plates 52 being welded or otherwise affixed to classifier portion 23.

The upper edge 53 of partition 46 is higher than the upper edge 54 of partition 47 and upper edge 54 is higher than the upper edge 55 of partition 48. Circular shields 56, 57 and 58 are fastened respectively to wall 40, partition 46 and partition 47 in spaced relation to the re spective upper edges 53, 54 and 55. Such circular shields extend over the tops of the respective passages 49, 50 and 51. The innermost partition 48 is provided with a skirt 59 which is of inverted conical shape. Skirt 59 extends downwardly a sufiicient distance to its lower edge 60 so that the inlets 21 of the return pipes 29 are at least partly behind the skirt 59. Moreover, the clear internal diameter of lower edge 60 is approximately the same as the outer internal diameter of chamber 38. Hence, oversize particles moving generally downwardly in annular re turn passages 49, St? and 51 and in the annular inverted conical space between the wall of portion 22 and skirt 59 are in generally separated relation to material from chamber 12 and pipe 36 discharged upwardly into the center of classifier 23 along the axis thereof, and further, in generally separated relation to additional gas moving upwardly from chamber 38 in the direction of the movement of such material. Such additional gas as may pass to the outer side of edge 60 tends to give some buoyant effect to oversize particles moving downwardly in the annular return passage so they more readily arrive at the inlets 21, whence such oversize particles with the gas therewith return through return pipes 20 to entry openings 3.8 for regrinding by the jets 11.

An independent variable speed motor drive 61 is adjustably mounted on a belt-tightening base 62. Motor 61 drives a pulley 63 to operate a bevel gear case and thrust bearing assembly 65 supported by a flange 64 at the top of the top vertical portion of pipe bend 43. Assembly n is centered in line with the axis of classifier 23 and rotatably supports a shaft 66 which is turned by the motor assembly 61 when the new device is in operation. Shaft 66 supports at difierent levels in classifier 23 a plurality of rotors 67 having radially extending arms 68. Each arm 68 may be of angle section and faced to rotate in the direction shown by the arrow in Figure 5. Thereby each edge 69 becomes a leading edge and in the rotation of rotors 67 by shaft 66 oversize particles are gathered within the bends of the arms 68 and move outwardly toward the outside of classifier 23 due to the centrifugal force which is more effective upon oversize particles.

Oversize particles reaching the outer ends of arms 68 in the respective tiers encounter a rearwardly and downwardly extending lug 70 which assists the rotors 67 in moving oversize particles generally downwardly. Thus, rotor 67 in the lowermost tier 71 will move oversize particles garnered by it into annular return passage 51 while the next higher rotor 67 in tier '72 will move oversize particles into annular return passage 50, while uppermost rotor 67 in tier 73 will move oversize particles into annular return passage 49. Such oversize particles and accompanying gas move generally downwardly and are sent back through return pipe members 20 to jets 11 for regrinding if they remain oversize despite such attrition as may occur in the course of their generally downward movement. Oversize particles which do become reduced to a sufiicient extent in the course of any generally downward movement would tend to be picked up by the additional or strip gas flowing into classifier 23 from chamber 38 and in that sense would be reclassified without having to return to the jets 11, thereby saving energy and avoiding overfineness or non-uniformity in the final product.

The outermost ends of the rotor arms 68 extend through the clear spaces between the respective upper edges of the respective partition and the lower edges of the respective shields covering the upper ends of the respective annular return passages, as shown in Figure 1. Thereby, there is plural classification as material from the impact grinding chamber 12 ascends in classifier 23 and such classification furthermore is controllable through the variable speed of motor 61, the gas volume input into the new device through jets 11 and inlet 39, the quantity and character of solids fed from hopper 34 and other factors which ,will be understood by those skilled in the impact pulverizer field. Furthermore, the new device may be suitably insulated as will also be well .understood with respect to the portions thereof where heat transfer is to be maintained at a minimum.

A further classification of oversize particles which may remain in material ascending in classifier 23 may be performed adjacent the top of classifier 23. As shown more especially in Figure 4, the top edge of wall 40 is provided with notches 74 which in conjunction with head 41 constitute circumferentially spaced openings 75 around the top of wall 40. A ring 76 surrounds the outer side of wall 40 at the top thereof within an annular manifold chamber 77. Ring 76 is slidable relative to the outside of wall 40 in an axial direction under the influence of nuts '78 which when turned adjust the height of ring 76 to adjust the size of the openings 75 by regulating the vertical height of those openings. Studs 79 extend between ring 76 and nuts 78. Studs 79 have their upper portions threaded. Such upper portions extend through corresponding openings in head 41 so that as nuts 78 are turned ring 76 is correspondingly raised or lowered depending upon the direction of turning of such nuts 78.

The sides and bottom of manifold chamber 77 are fastened to the outside of wall 4d at the top of classifier 23 as shown. Openings 80 are provided in such bottoms to communicate with a withdrawal pipe 81. In the embodiment shown, there is one such withdrawal pipe on each side, 180 apart, of the new device. The withdrawal pipes 81 join in a T-fitting 82 leading to a suction pipe 83, in the embodiment shown, of a blower 84 having a shaft 85 which is turned by a variable speed motor (not shown) suitable to the particular operation in which the new device is to engage at the time being. A delivery pipe 87 from blower 84 returns oversize particles with drawn through adjusted opening 75 and manifold '77 to portion 22 through opening 83. Opening 88 is above chamber 38 and discharge end 37 of pipe 36 and also is adjacent edge 69 of skirt 59. Hence, the stream entering portion 22 from pipe 87 is subject to renewed classification for removal of any particles of appropriate fineness and for return of oversize particles to inlets 21 and return pipes 20 for regrinding by the jets 11.

The plural rotor tiers, the adjustable power means for turning those tiers, the further adjustable means for classification adjacent the top of classifier 23 and the controls exercisable through the gas inputs into the nozzles 14 and chamber 38 with the respective circuits in the new device provide a new construction of extraordinary flexibility in the impact grinding field. As an example, graphite may be ground to a maximum size, for example, of eight microns with complete assurance of a satisfactory size and uniform product. Other and diverse materials may as readily be ground to the desired fineness or coarseness with similar assurance of satisfactory final product.

Various changes in the embodiment illustrated may be made without departing from the scope of my invention or the scope of the appended claims.

I claim:

1. In a jet pulverizer, in combination, an enclosed impact grinding chamber, jets discharging gas and solids in impact relation into said chamber, said jets having a separate entry opening for each thereof, a discharge pipe extending into said chamber for material leaving said chamber, a classifier into which said discharge pipe discharges, rotor means in said classifier to cause oversize particles in said material to move toward the outside of and downwardly in said classifier, said rotor means being spaced above and separated from said discharge pipe, means for removing oversize particles from said classifier in substantially separated relation to material entering said classifier from said discharge pipe, and means having adjustable openings positioned around the upper portion of said classifier to remove finer oversized particles therefrom.

2. In a classifier adapted to receive gasborne particles from a pulverizer, apparatus comprising, in combination, means for discharging said particles into the bottom of said classifier, means for removing finer particles adjacent the top of said classifier, a tubular partition spaced inwardly from but adjacent the interior of said classifier, the axes of said classifier and partition being vertical, a deflector rotor extending across the top of said partition and above the space between said partition and said wall, means for rotating said rotor to cause coarser particles to pass downwardly into said space between said partition and the interior of said classifier, means for removing said coarser particles from said last-mentioned space, peripheral openings in said classifier above said rotor, and means for withdrawing gaseous medium therethrough to remove particles of intermediate coarseness from said classifier.

3. In a classifier adapted to receive gasborne particles from a pulverizer, apparatus comprising, in combination, means for discharging said particles into the bottom of said classifier, means for removing finer particles adjacent the top of said classifier, means for introducing a gaseous strip medium into said classifier alongside the gasborne particles received thereby, a tubular partition spaced inwardly from but adjacent the interior of said classifier, the axes of said classifier and partition being vertical, a deflector rotor extending across the top of said partition and above the space between said partition and said wall, means for rotating said rotor to cause coarser particles to pass downwardly into said space between said partition and the interior of said classifier, means for removing said coarser particles from said lastmentioned space, means for discharging said coarser particles from said classifier, adjustable peripheral openings in said classifier above said rotor, means for withdrawing gaseous medium through said peripheral openings to remove particles of intermediate coarseness from said classifier, and means for returning said particles of intermediate coarseness to the lower part of said classifier.

4. In a jet pulverizer, in combination, an impact grinding chamber, jets discharging gas and solids in impact relation into said chamber, said jets having an entry opening, a discharge pipe for material leaving said chamber, a classifier connected to said discharge pipe adjacent said impact grinding chamber, means for supplying additional gas to said classifier adjacent the zone of entry of said material into said classifier, rotating means in said classifier to cause oversize particles in said material to move toward the outside of said classifier, and means for removing oversize particles from said classifier in substantially separated and outward relation to material entering said classifier from said discharge pipe. I

5. In a jet pulverizer, in combination, an impact grinding chamber, means for feeding fresh material to be ground into said first-named chamber, a pair of jets in opposed alignment discharging gas and solids into said chamber, said jets having an entry opening for particles, an upwardly extending discharge pipe for material leaving said chamber, a classifier receiving material from said chamber through said discharge pipe, an annular removal passage around the wall of said classifier for oversize particles, a rotor having radially extending arms in said classifier to move oversize particles toward the wall of said classifier and downwardly through said return passage, means to turn said rotor, means for supplying additional gas to said classifier around said discharge pipe, an annular chamber adjacent the top of said classifier, said annular chamber having adjustable openings communicating with the interior of said classifier, and fluid-conveying means extending between said annular chamber and a portion of said pulverizer adjacent said impact grinding chamber to withdraw finer oversized 6 particles by suction. from the top of said: classifier for delivery to said portion.

6. In a jet pulverizer, in combination, an impact grinding chamber, jets discharging gas and solids in opposed relation into said chamber, said jets having. entryopen,- ings for particles, at discharge pipe for material leaving said chamber, said discharge pipe extending upwardly and being ofiset from the axes of said jets, a classifier connected to said discharge pipe to receive material from said chamber, a rotor in said classifier to cause oversize particles in said material to move toward the outside of said classifier, independent means for turning said rotor, an annular return passage around the outer wall of said classifier for oversize particles, and return pipe members connecting said annular passage and said entry openings, said members having their inlets at least partly separated from material entering said classifier from said discharge pipe.

7. In a jet pulverizer, in combination, an impact grind,- ing chamber, means for feeding fresh material to be ground into said chamber, jets discharging gas and solids in opposed relation into said chamber, said jets having an entry opening for particles, a discharge pipe for material leaving said chamber, said discharge pipe extending upwardly, a classifier into which said discharge pipe empties material from said chamber, a rotor in said classifier to cause oversize particles in said material to move toward the outside of said classifier, means independent of said jets for turning said rotor, an annular partition defining return passage around the outer wall of said classifier for oversize particles, a return pipe connecting said annular passage and said entry opening, and an inverted conical skirt connected to the lower part of said partition, said skirt extending downwardly a distance sufiicient to shield at least the upper end of said return pipe.

8. In a jet pulverizer, in combination, an impact grinding chamber, means for feeding fresh material to be ground into said chamber, jets discharging gas and solids in impact relation into said chamber, said jets having an entry opening, a discharge pipe for material leaving said chamber, a classifier connected to said discharge pipe to receive said material upwardly through the general cen ter thereof, movable means to cause oversize particles in said material to move toward the outside of said classifier, a plurality of return passages in said classifier for said oversize particles, said passages being in substantially separated relation radially and vertically relative to material entering said classifier from said discharge pipe.

9. In a jet pulverizer, in combination, an impact grinding chamber, jets discharging gas and solids in impact relation into said chamber, said jets having an entry opening, a discharge pipe for material leaving said chamher, a classifier connected to said discharge pipe to receive said material, outwardly extending arm means to cause oversize particles in said material to move toward the outside of said classifier, a plurality of concentric return passages for said oversize particles, said passages being in substantially separated relation relative to material entering said classifier from said discharge pipe, said return passages being operative at different levels in said classifier, and a further return passage outside of said classifier.

10. In a jet pulverizer, in combination, an impact grinding chamber, jets discharging gas and solids in impact relation into said chamber, said jets having respective entry openings, a discharge pipe for material leaving said chamber, a classifier connected to said discharge pipe, annular means for supplying additional gas to said classifier adjacent the zone of entry of said material into said classifier, movable outwardly and downwardly deflecting means in said classifier to cause oversize particles in said material to move toward the outer Wall of said classifier, and means for returning oversize particles to said entry openings in substantially separated and outward relation to material entering said classifier from said'discharge pipe, said last-mentioned means including an adjustable suction-control passage connected to said classifier to remove other oversize particles from an upper portion of said classifier to a lower portion thereof.

11. In a jet pulverizer, in combination, an impact grinding zone, jets discharging gas and solids into said zone, a classifier adjacent said zone in direct communication therewith, movable means within said classifier to cause oversize particles in material from said zone to move toward and generally downwardly along the radially outer portion of the inside of said classifier, means for generally separating the streams of material entering said classifier from said zone and the streams of oversize particles moving downwardly, means for returning said oversize particles to said jets for regrinding, independent means adjacent the upper portion of said classifier for removing further oversize particles, and an outlet radially inwardly of said last-mentioned means for removing particles of proper size from said jet pulverizer.

12. In a jet pulverizer, in combination, an impact grinding zone, jets discharging gas and solids into said zone in opposed grinding relation, a classifier adjacent said zone in direct communication therewith, means for supplying additional gas to said classifier in a generally upward direction, said means being adjacent the place of discharge of said material from said zone into said classifier, variable speed rotor means within said classifier to move oversize particles in material from said zone toward and generally downwardly along the radially outer portion of the inside of said classifier, peripheral adjustable fiush opening means adjacent the top of said classificr for removing further oversize particles and returning them for further classification and rejection as the case might be, and means for eventual return of all oversize particles to said jets for regrinding.

13. In a jet pulverizer, in combination, an impact grinding zone, jets dsicharging gas and solids into said zone in opposed grinding relation, a classifier adjacent said zone in direct communication therewith, rotor means within said classifier to move oversize particles in material from said zone toward and generally downwardly along the peripherally outer portion of the inside of said classifier in generally physically separated relation to upwardly moving particles in said classifier; further means adjacent the top of said classifier for removing further oversize particles and returning them to said classifier adjacent the inlet end thereof, means for varying the classifying performed by said two first-mentioned means, and means for supplying additional gas to said classifier in a generally upwardly direction, said last-mentioned means being adjacent the place of discharge of said material from said zone into said classifier.

14. In a jet pulverizer, in combination, an impact grinding chamber, means for conveying solids to be ground into said chamber, a pair of jets in opposed alignment discharging gas and solids into said chamber, said jets having an entry opening for said particles, an upwardly extending discharge pipe for material leaving said chamber, a generally vertical classifier receiving material from said chamber through said discharge pipe, a plurality of concentric partitions forming a plurality of annular return passages around the wall of said classifier for oversize particles, the respective outer of said partitions having its uppermost-edge respectively higher, a circular shield above each such passages, a rotor having radially extending arms in said classifier to move oversize particles toward the wall of said classifier-and downwardly through a return passage, means extending along the axis of said classifier to turn said rotor, and return pipes connecting said annular return passage and said respective entry openings.

v 15. In a jet pulverizer, in combination, an impact grinding chamber, means for conveying solids to be ground into said chamber, a pair of jets in opposed alignment discharging gas and solids into said chamber, said jets having an entry opening for said particles, an upwardly extending discharge pipe for material leaving said chamber, a generally vertical classifier receiving material from said chamber through said discharge pipe, a plurality of concentric partitions forming a plurality of annular return passages around the wall of said classifier for oversize particles, the respective outer of said partitions having its uppermost edge respectively higher, a rotor having radially extending arms in said classifier to move oversize particles toward the wall of said classifier and downwardly through a return passage, means extending along the axis of said classifier to turn said rotor, and return means connecting said annular return passage and said respective entry openings, the innermost of said partitions having a skirt substantially to separate material discharged into said classifier from said discharge pipe and oversize particles moving downwardly through said return passages for regrinding.

16. In a jet pulverizer, in combination, an impact grinding zone, jets discharging gas and solids in impact relation into said zone, a classifier adjacent said zone in direct communication therewith, means for supplying additional gas to said classifier adjacent to material entering said classifier from said zone, means within said classifier to move oversize particles generally toward and downwardly along the radially outer portion of the inside of said classifier, means for generally separating material and additional gas entering said classifier from said zone and said first-mentioned means from such oversize particles moving generally downwardly, means at least partly behind said last-mentioned means for returning oversize particles to said jets for regrinding, adjustable opening means adjacent the top of said classifier for withdrawing further oversize particles out of said classifier, and means for returning said further oversize particles to said classifier adjacent said first-mentioned means.

References Cited in the file of this patent UNITED STATES PATENTS 1,325,676 McKelvey Dec. 23, 1919 1,595,257 Stebbins Aug. 10, 1926 1,882,329 Kreisinger Oct. 11, 1932 1,935,344 Andrews Nov. 14, 1933 1,953,058 Andrews Apr. 3, 1934 2,200,822 Crites May 14, 1940 2,561,564 Crites July 24, 1951 2,624,516 Andries Ian. 6, 1953 OTHER REFERENCES Majac I et Pulverizers, the new art in industrial pulverizing. Publication of Majac Engineering Company, 189 Freeport Road, Blaw.

Nox (Pittsburgh District), Pennsylvania, one large sheet showing sectional view of the Majac Pulverizer the product of better engineering Know How, folded into two double page halves. Dated May 26, 1953 by Library United States Patent Ofiice Stamp.

UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION Patent Nos 2 934376 April 26 1960 George 1V1a Croft It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

es cited under the heading Column 8 list of referenc d 63 should appear as shown below "OTHER REFERENCESM lines 62 an instead of as in the patent:

Freeport Road Blawnox (Pittsburgh District) 0 Pennsylvania one large Signed and sealed this 27th day of September 1960,

(SEAL) Attest:

KARL Ho AXLINE Attesting Officer ROBERT C. WATSON Commissioner of Patents 

